1. Field of the Invention
The invention relates to a system for joining flat, relatively thin members that adjoin one another along their narrow face, the members having grooves incorporated into the narrow faces that are parallel to the surface and have groove walls that are parallel to each other, and the joining element being inserted into the grooves of two adjacent members and bridging the partition gap between the members in the manner of an external tongue.
2. Background Description
Configurations of this kind have the advantage that all members are formed completely the same; that is, it is not necessary to ensure that a side with a groove always faces a side with a tongue, such members also being substantially easier to manufacture. In the installation of this known configuration, external tongues are used, whereby the flat member to be attached may be attached without regard to its edge configuration. These known configurations have the disadvantage that, when installing them, there must be two gluing operations at each plate abutment because the external tongue has to be anchored with both longitudinal edges, namely once on a plate-like member and with the other longitudinal edge in the other member.
In order to generally avoid gluing at the installation site, disposing detent elements in the area of the tongue-and-groove joint in such a manner that projections provided on the tongue snap into corresponding recesses of the groove walls when the flat members that are to be arranged next to each other are joined is already known. However, in these known designs, especially in those in which the flat joining elements are formed from the same material as the plates themselves, one must ensure that the groove walls are elastic enough that the front edges of the groove walls in the direction of insertion can be moved far enough away from each other that the projections provided on the tongue can be moved in between the front edges of the groove walls without causing damage. In members formed from fiber plates, deficient quality in the fiber plates can in fact cause the groove walls to break through or break away, causing this member to then be unusable. This is especially true if substantial forces are exerted on the groove walls because of a steep inclination of the projections when joining the narrow faces of the members, as is the case, for example, in European Patent Application Publication no. 813 641.
Furthermore, providing snap-fit elements made of synthetic material on the back side of the panels whereby the narrow faces of the members are provided with gradations that engage within each other when the plates are fit together was already known. That plate on which the elastic snap-fit element is mounted forms a “groove” together with the stepped wall in which the projection of the step of the adjacent plate is insertable in the manner of a “tongue”. That plate on which the step to be inserted as a “tongue” is provided has a recess on the back side in which the snap-fit element of the additional snap-fit organ that is to be fastened to the other plate engages. A design of this type has the disadvantage, especially with thin plates, that only a little material is available for clamping the additional snap-fit organ, whereby the step flanks must absorb the forces that are required to move away the snap-fit element when joining together the plates. Although it is described within the context of this design that the member to be joined is swung “tongue-first” into the “groove” on the other member, this requires an appropriate amount of play between the step walls that run roughly parallel to the top surface, because otherwise the swinging in is not possible or is possible only when swinging away the snap-fit organ, which again exerts substantial forces on the steps. A design of this type emerges from WIPO patent 94/26999. However, such play permits limited movement on both sides, which is especially disadvantageous for floors.
Furthermore, incorporating tongue-and-groove joints made of synthetic material in the edges of the members, for example, by pouring them in during injection molding or otherwise incorporating them into the material in order to be able to absorb the spreading forces of the groove when joining the members, using not a wood-based material, but an elastic material. Such a design emerges from WIPO patent 94/01628, in which design the tongue is also slit along its longitudinal center plane, thereby enabling it to be slightly compressed. Designs of this type are not usable in terms of manufacturing technology with members that are based on wood materials, because in the process wall thicknesses that are too thin may result, which may easily lead to a danger of breakage when joining and also when shipment is not entirely proper.